Python-Asyncio API & SDK Docs 10.4.1

This guide walks you through a simple "Hello, World" application that demonstrates the core concepts of PubNub:

  • Setting up a connection
  • Sending messages
  • Receiving messages in real-time

Overview​

This guide helps you get up and running with PubNub in your Python application using the asyncio application programming interface (API). The Python-Asyncio software development kit (SDK) provides a simple interface for integrating PubNub real-time messaging into asynchronous Python applications. Whether you build a web service, desktop application, or Internet of Things (IoT) device, this guide shows you how to get started.

Prerequisites​

Before we dive in, make sure you have:

  • A basic understanding of Python and asyncio
  • Python 3.9 or later installed
  • A PubNub account (we'll help you set this up!)

Setup​

Get your PubNub keys​

First, get your PubNub keys:

  • Sign in or create an account on the PubNub Admin Portal.
  • Create an app (or use an existing one).
  • Find your publish and subscribe keys in the app dashboard.

When you create an app, PubNub automatically generates a keyset. You can use the same keyset for development and production, but we recommend separate keysets for each environment to improve security and management.

Install the SDK​

SDK version

Always use the latest SDK version to have access to the newest features and avoid security vulnerabilities, bugs, and performance issues.

There are several ways to install the PubNub Python SDK:

Use pip​

Install with pip:

pip install pubnub

Source code​

Clone the GitHub repository:

git clone https://github.com/pubnub/python

View the supported platforms for more information about compatibility.

Steps​

Initialize PubNub​

Create a Python script with the following content. This is the minimum configuration required to send and receive messages with PubNub.

Replace the demo keys with your app's publish and subscribe keys from the Admin Portal.

# Import required modules
import asyncio
from pubnub.pnconfiguration import PNConfiguration
from pubnub.pubnub_asyncio import PubNubAsyncio

# Set up PubNub configuration
pnconfig = PNConfiguration()
pnconfig.subscribe_key = 'demo'  # Replace with your subscribe key
pnconfig.publish_key = 'demo'    # Replace with your publish key
pnconfig.user_id = 'asyncio-user'

# Create a PubNub instance
pubnub = PubNubAsyncio(pnconfig)

For more information, refer to the Configuration section of the SDK documentation.

Set up event listeners​

Listeners help the application react to events and messages. You can implement custom logic to respond to each type of message or event.

Use a status listener to handle connection status changes:

from pubnub.pubnub_asyncio import SubscribeListener

# Create a custom listener for status events
class StatusListener(SubscribeListener):
    def status(self, pubnub, status):
        # This method is called when the status of the connection changes
        print(f'Status: {status.category.name}')
    
    # We're not implementing the message handler here as we'll use a subscription-specific handler

# Add the listener to your PubNub instance
status_listener = StatusListener()
pubnub.add_listener(status_listener)

For more information, refer to the Listeners section of the SDK documentation.

Create a subscription​

To receive messages sent to a particular channel, you need to subscribe to it. You do this by creating a subscription and activating it:

# Define the channel you want to subscribe to
my_channel = 'example'

# Create a subscription for the channel
subscription = pubnub.channel(my_channel).subscription()

# Set up a message handler
subscription.on_message = lambda message: print(f'Message received: {message.message}')

# Subscribe to the channel
subscription.subscribe()

print(f'Subscribed to channel: {my_channel}')

The SDK offers multiple ways to handle incoming messages. A subscription-specific handler (as shown above) is recommended for most applications.

For more information, refer to the Subscribe section of the SDK documentation.

Publish messages​

When you publish a message to a channel, PubNub delivers that message to everyone who is subscribed to that channel.

A message can be any type of JavaScript Object Notation (JSON)-serializable data (such as objects, arrays, integers, strings) that is smaller than 32 KiB.

import asyncio
from pubnub.exceptions import PubNubException

async def publish_message():
    # Wait for a moment to ensure the subscription is active
    await asyncio.sleep(1)
    
    # Create a message
    message = {
        'msg': 'Hello from PubNub Python-Asyncio SDK!'
    }
    
    try:
        # Publish using result() which directly returns the result (or raises an exception)
        result = await pubnub.publish().channel(my_channel).message(message).result()
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The Python-Asyncio SDK provides two ways to handle callbacks:

  • Using result() which returns just the result and raises exceptions directly
  • Using future() which returns an envelope with both result and status objects

Run the app​

To test the code, save it as pubnub_asyncio_demo.py and run it from your terminal:

python pubnub_asyncio_demo.py

When you run the application, you should see output similar to the following:

Subscribed to channel: example
Status: PNConnectedCategory
Message received: {'msg': 'Hello from PubNub Python-Asyncio SDK!'}
Published message with timetoken: 16967543908123456

You receive the message that you published because the client subscribes to the same channel.

Complete example​

import asyncio
from pubnub.exceptions import PubNubException
from pubnub.pnconfiguration import PNConfiguration
from pubnub.pubnub_asyncio import PubNubAsyncio, SubscribeListener

# Step 1: Initialize PubNub with configuration
pnconfig = PNConfiguration()
pnconfig.subscribe_key = 'demo'  # Replace with your subscribe key
pnconfig.publish_key = 'demo'    # Replace with your publish key
pnconfig.user_id = 'asyncio-user'
pnconfig.ssl = True              # Enable SSL for secure connection

pubnub = PubNubAsyncio(pnconfig)

# Step 2: Create a status listener
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Troubleshooting​

If you don't see the expected output, here are some common issues and how to fix them:

IssuePossible Solutions
No connection message
  • Check your internet connection.
  • Verify your publish and subscribe keys are correct.
  • Make sure you're not behind a firewall blocking PubNub's connections.
Message not received
  • Double-check that you're subscribed to the correct channel.
  • Verify that the message was actually sent (check for any error messages).
  • Make sure you're waiting long enough for the message to be delivered.
Import errors
  • Ensure you've installed the PubNub package correctly.
  • Check that you're using a compatible version of Python.
  • Make sure all imports are correct.

For more detailed troubleshooting information, refer to the Troubleshooting section of the SDK documentation.

Next steps​

Great job! 🎉 You've successfully created your first PubNub application with Python-Asyncio. Here are some exciting things you can explore next:

  • Add Channel Groups to organize your channels.
  • Implement typing indicators and read receipts.
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